Synchromesh transmission



Feb. 10, 1948..) new; v 2,435,929

SYNCHROMESH TRANSMI SS ION Filed Jan. 22, 1945 3 Sheets-Sheet 1 Feb.'l0, 1948. co 2,435,929

SYNCHROMESH TRANSMISS ION Filed Jan. 22, 1945 3 Sheets*Sheet 2 W fl? 5% 4,3,6, Y Clllornys v Jnuenfor WJf/enko 4 R. s. PLEXICO 2 SYNCHROMESH TRANSMISSION Filed Jan. 22, 1945 3 Sheets-Sheet 3 'Jnoenfor Patented Feb. 10, 1948 2,435,929

UNITED .STATES PATENT OFFICE SYNCHROMESH TRANSMISSION Robert S. Plexico, Royal Oak, Mich" ass gnor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 22, 1945, Serial No. 513,821

This invention relates to a change speed transmission for vehicles providing four forward speed ratios and one reverse ratio, the shift into each of the three highest ratios being made with the aid of synchronizingmechanism.

The object of the invention is primarily to provide synchromesh for that driving ratio next above low speed. Other obiects are concerned wtih novel structure by which the major object is attained and by which also there may be attained other objects and advantages which will be understood from the description which folows:

In the accompanying drawing,

Fig. 1 is a vertical longitudinal section through the change speed transmission.

Fig. 2 is a view as seen from line 2-2 of Fig. 1.

Fig. 3 is a section on the broken line 3-3 of Fig.

Fig. 4 is a-section as indicated by line 44 of Fi 3.

Fig. 5 is a view in elevation partly broken away and in section, the plane of the section being marked 55 on Fig. 3.

Fig. 6 is a perspective of a detail.

Fig. 7 is a view in elevation partly broken away and in section to show a trap device to collect and retain foreign matter, see line 1--'1 on Fig. 1.

Fig. 8 is a perspective view of the plate seen in section in Fig. 7.

Referring by reference numerals to the drawing, a clutch shaft H from the engine and clutch enters the transmission housing i3 where it is sup ported by bearings i5. Within the housing. or gear box, shaft ii carries a gear I1, a ring of 3 Claims. (Cl. '14339) box the cone 23 serves to synchronize the rates of rotation so that shaft 21 may be clutched without noise to rotate Jointly with shaft I l.

Gear I1 on shaft Ii constantly drives gear 43 keyed to a countershaft 46 joumaled in the gear casing walls as shown. 5A countershaft gear 45 clutch teeth i9 and it ends in a tapered cone 2i.

A synchronizing cone 23 with teeth 25 is adapted to rotate on surface 2 I.

A transmission shaft 21 extends from a pilot bearing 29 within the end of shaft II to and through bearings 3! in the rear wall of the gear box. Rigid with shaft 21 is a ring 33 peripherally formed to slidably guide a clutch ring 35. The internal teeth of the ring 35 are to mesh successively with clutch teeth-25 and i9. Rotatably mounted on shaft 21 is a gear 31. As in the case of the end of shaft ii, gear 31 has gear teeth 39, clutch teeth and a tapered end as shown together with a synchronizing cone with clutch teeth. These and other details need not be further described for the reason that no patentable novelty is being claimed for this mechanism by itself. -Between the two synchronizing cones and the ring 35 is a spring device 41 so positioned that when ring 331s moved toward the engine end of the gear is in constant mesh with gear teeth 39. When ring 35 is moved rearwardly it looks gear 31 to shaft 21 with the aid of the synchronizing means whereby shaft ll drives shaft 21 at a speed ratio of less than unity. This may be called third speed, fourth speed being the expression used for the direct drive of shaft 21.

The countershaft carries a gear 41 in constant mesh with a gear 49, gear 49 withits hub 5i being rotatably supported on shaft 21. Slidable but non-rotatable on shaft 21 is a gear 53. It has internal teeth adapted to engage external teeth 91 on the hub 5| of gear 49 when moved toward gear 49. A synchronizing ring 6| is carried within a forward extension 63 of gear 53 and retained by a ring 65. There are the usual tapered faces on the gear extension and ring 6i. Ring 6| has a plurality of axial extensions 51 shaped as shown by Fig. 2. Gear 49 has apertures 69 one for the passage of each extension 61. As gear 53 moves forwardly the ring 6! is carried with it. If gears 49 and 53 have unlike rates of rotation the ends of extensions 61 engage on one side or the other of the tapered faces 1| leading into the apertures 69 and resist further movement until the frictional resistance between the tapered surfaces effects synchronization. Then the ends 61 pass freely through the openings 69 and the teeth 55 and 51 engage. This second speed drive is theretore through gear train "-43 and 41-49 the latter now locked to shaft 21.

Low or first speed is obtained by moving gear 53 toward the rear. Itcarries the synchronizing device with it, the latter having no function in connection with low speed. -As it moves toward the rear gear 53 slides into mesh with countershaft gear 13.

Reverse drive is effected by a pair of spaced gears 15 and 11 on a third shaft 19. When these gears are moved jointly, gear 15 is made to mesh with a countershaft gear 19 and gear 11 to mesh with gear 53. Reverse drive is therefore through gear trains l1-43, 19-15 and 1153.

The mechanism for shifting the clutches and gears to get the several driving ratios is mounted in the cover 8|. Into the dome of the cover there projects a manually operable lever 83 having a fulcrum, not shown. Within the cover are three rods or rails 85, 81, 89. The cover is formed with regions such as 9| and 99 to guide these rails as they reciprocate. Plugs 95 close openings in the cover through which openings the rails are assembled. This arrangement prevents loss of oil which might occur if the rails were slldably supported in end walls of the casing. The rails have notches 91 to receive detent balls 99 projecting from cover pockets Il containing springs I03 to yieldably hold the rails in positions of adjustment. Carried by rail 85 is a lever engaging head I05 and a fork I01 the lower end of which engages a groove in ring 35. Rail 81 carries a second lever engaging head I09 located adjacent head I05. Rail 81 also carries a fork I I I axially spaced from head I09 and embracing gear 53. Rod 89 carries a head II3 directed laterally over rod 81 and terminating adjacent head I09. Rod 89 also has a projection II5 operatively engaging the upper end of a lever I11 pivoted to the casing at II9. its lower end being received within a collar of shaft 16 whereby gears 15 and 11 are moved. The three heads are notched as at I2! to selectively receive the end of lever 83 as it moves in one plane prior to being moved in a second plane to reciprocate one or another of the rods and engage the clutches or teeth as de scribed.

The mechanism to prevent the shift of any other than the selected rail is a plate I22. It slides along an inner overlying cover surface as shown by Fig. 4. It is guided by pins projecting through slots I23 and I25 of the plate and extending into the cover, the heads I21 serving as supporting means. Tongues I29, I3I are bent down into a plane below the plane of the plate. These tongues are dimensioned to slide into rail head slots I2I. Plate I22 has a transverse slot I33 for the passage of the end of lever 83. Overlying and secured to plate I22 is another transversely slotted plate I35. The lever 83 passes through this slot. In one side of the slot of plate I35 is a bent up tongue I31. In a cover opening I39 is slidably mounted a pin MI backed by a spring I43. In that position of the change speed mechanism wherein the lever is in the position shown by Fig. 4, the tongue I31 lies closely adjacent the end of pin I4I. When the lever is selectively moved to enter the notch of head I05 it moves parts I35 and I22 with it. Tongue I3I while remaining in the notch of head II3 also enters the notch of head I09. Tongue I3l therefore holds both rails 89 and 81 when tongue I29 slides out from the notch of head I05. Then lever 83 may be moved in the slots of plates I22 and I35 to move rail 85 lengthwise of the transmission and engage the clutches for fourth speed or for third speed. In the position shown by Fig. 4 rail 85 is held by tongue I29 and rail 89 by tongue I3I. Rail 81 may be moved to obtain second speed or low speed depending upon its direction of movement. If the lever is moved to engage the notch of head H3 tongue I29 locks rails 85 and 81. Lest, in the selecting movement, the lever 83 be moved beyond the notch of head I09 when a shift to the low or second speed is desired and into head II3 the tongue I31 engaging pin I4I resisted by spring I39 warns the operator of the excessive lever movement.

It will be noticed that fork III embraces low speed driving gear 53. The rotation of this gear may tend to rotate fork III and its shaft 81 the more especially as some appreciable force is applied by the fork against the side of the gear in the act of synchronizing. Any such rotation 4 might interfere with a free relationship between thehead I09 and the interlocking plate. To prevent any rotation of rail 91' the fork III has a lateral arm I99 forked to straddle rail 99 as best by contact. of parts of I09 and Ill, any rotation of rail 89. By this means the correct position of the interlocking plate I22 and the heads I09 and H9 is effected. Head I05 and rail cannot rotate because fork I01 embraces ring 35.

Extending transversely across the gear housing near the bottom thereof is a plate I5I with tongues I53 bent down therefrom. Preferably the end of plate I5I has a part I55 resting on a casing surface and a bent tongue I51 which may be welded to a nut I59 engaged by a bolt I5I which serves to hold a cover I83. The enclosure serves to trap chips and foreign matter driven by the rotating gears through the openings. A conventional plug I65 will provide for draining oil and the removal of sediment. The resiliency of tongue I51 is such that the attachment by the bolt I5! is sufficient to hold the chip plate in the position shown.

I claim:

1. In a change speed transmission, a driving shaft, a parallel driven shaft, a first gear rigid with thedriving shaft, 9. second gear rotatably supported on the driven shaft and in constant mesh with said first gear, a third gear slidably but non-rotatably mounted on the driven shaft, clutch teeth on said second and third gears, a. pair of synchromesh elements both carried by said slidable gear, one only being rigid with the gear, the other being rotatable and having axial projections, said second ear having apertures with beveled margins adapted by the cooperation of said beveled margins with said movable synchronizing elements to effect synchronization, said projections thereafter movable thro h said apertures as said clutch teeth engage.

2. The invention defined by claim 1, said sec- 0nd gear having an elongated hub, its clutch teeth being formed externally on said hub and said movable synchronizing element overlying said hub.

3. The invention defined by claim 1, said driving shaft having a fourth gear rigid therewith and said third gear adapted to slide into mesh with said fourth gear, carrying the pair of synchromesh elements therewith.

ROBERT S. PLEXICO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED I STATES PATENTS 

